Now that we know who our final four contestants are on The Biggest Loser, it's time to determine which two contestants will definitely move on to the finale, and which two contestants will fall below the yellow line, leaving America to vote for the third finalist to compete for the grand prize of $250,000.

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But before anything else, Ashley, Daris, Koli and Michael first head home for 30 days to prepare for a marathon--which isn't exactly working in their favor since some of the contestants are having a hard time focusing on their goal when surrounded by distractions. At least, one contestant gets a special visit from chef Curtis Stone.

Did their efforts at home pay off? We find out back at the ranch where the players return to run the 26.2 miles marathon. Supporting them are family members and past Biggest Loser contestants, including season 5 winner Ali Vincent, Season 2 winner Matt Hoover, and Season 7 contestants Mike Morelli and Sione Fa. Surprisingly, the winner of the marathon breaks a new record.

But the real test comes at the final weigh-in, where one contestant unexpectedly gains 2 pounds.